This invention relates to conveying apparatus for heat treatment furnaces in the case of which the material that is to be treated is transported by means of conveyor belts, straps made of wire links or conveying boxes.
Known supports of conveyor belts or wire links are made in such a way that an endless belt is driven by a roller on the one side and is reversed by a roller on the other side.
Such an arrangement has the disadvantage that the conveyor belts or the straps of wire links are subjected to a great tension load. Since in the case of higher temperatures, the strength of the material drops very considerably, it is extremely important to keep the tension load of the belt small, in order to achieve a sufficient useful life for the belt.
Another known belt driving arrangement attempts to eliminate the above-mentioned disadvantage. In this apparatus, the conveyor belt rests on a moveable plate. This plate is moved forward and backward, whereby the belt is driven in the forward movement and during the backward stroke, the plate is pulled away from under the belt.
As a result of that, tension on the belt during the feed is avoided, during the backward thrust, when the plate is withdrawn from under the belt, such a tension on the belt cannot be avoided.
For the furnace transportation of boxes or shuttles, pushing through or driving is used as a known process. The disadvantage in the case of this process is quite obvious. The pushing forces required for the individual boxes are additive, so that by summation considerable force must be exerted on the boxes, which might result in the case of higher temperature in the deformation of boxes.
The present invention makes it possible to avoid the main disadvantage of the known conveying apparatuses, namely the high mechanical stress on the conveying belts or boxes. This object is achieved by the fact that the propelling force is made uniformly effective along the entire furnace and does not, as in the case of the conveyor belt, only act locally by the driving roll or in the case of pushing through furnaces by locally concentrated pushing.
The problem on which the invention is based is to distribute the driving force uniformly over the conveying path and the objects or articles to be conveyed, such as conveyor belts, straps of wire links, boxes, shuttles, plates or jointed bands subdivided into individual boxes.
According to the invention, this problem is solved by imparting the driving force to the articles that are to be conveyed by two or more rolls disposed with their longitudinal axes at an acute angle in relation to the direction of transportation, which rolls move at the same speed of rotation, but in an opposite rotational direction. The rolls can be developed solid or hollow and they have their longitudinal axes slightly inclined in the direction of conveyance. However, the longitudinal axes of the rolls always lie in one plane. A single endless flexible means encircles both of the rolls.